The present system and method relate generally to hybrid motor vehicles, and more particularly, to a system and method for establishing a shift point strategy in a hybrid motor vehicle.
Automobile manufacturers are constantly working to improve fuel efficiency in motor vehicles. Improvements in fuel efficiency are typically directed toward reducing weight, improving aerodynamics, modifying power inputs, and reducing power losses through the vehicle powertrain. However, the need to improve fuel efficiency is commonly offset by demands to provide enhanced comfort, power, and convenience to the vehicle operator. As an example, manually-shifted transmissions are more fuel efficient than automatic transmissions due to lower parasitic losses. However, a vast majority of domestic motor vehicles, for example, are equipped with automatic transmissions due to the increased operator convenience they provide.
In motor vehicles equipped with automatic transmissions, adjustments may be made to the timing of the gear shifts to vary the vehicle's fuel consumption characteristics, acceleration characteristics, and the like. Traditionally, a gear shift schedule map used in the control apparatus for the automatic transmission is determined at developing stage of a vehicle to establish shift points of a transmission based on the fuel consumption and acceleration characteristics of the engine. According to this method, it is possible to control the shift characteristics of the transmission in real time with a computer having a slow calculating speed since data necessary for control can be read out from the gear shift schedule map.
However, in recent times, vehicle manufacturers have been working to develop “hybrid” electric vehicles, which include an internal combustion engine and an electric or hydraulic motor, to provide a reduced level of pollutants when compared to traditional internal combustion engines. The ability of the recently developed hybrid electric vehicles to use one or both of the motor and the engine presents a number of issues for the development of a transmission shift point strategy. More specifically, formation of a pre-determined shift-point map is more difficult with hybrid vehicles due to the uncertainty introduced by often having multiple inputs providing torque to a vehicle driveline.